Pictures produced by a semiconductor image sensor may show slight non-uniformities from pixel to pixel, which can be caused by local temperature differences in the sensor chip, because leakage current and responsivity of a photodiode depend on the temperature. To avoid this problem, image sensor chips are preferably operated at a constant, spatially homogeneous temperature. Usual methods of maintaining a spatially and temporally constant temperature, especially by heating or cooling the whole image sensor chip, may not be appropriate to obtain optimal temperature conditions, especially if photo sensors are integrated in the vicinity of components generating heat.
U.S. Pat. No. 7,480,006 B1 discloses an integrated circuit package including a substrate with a surface disposed to receive an image sensor chip and with a heater element positioned underneath a sensor area of the image sensor chip.
U.S. Pat. No. 6,046,433 A discloses an integrated circuit die containing a metal heater resistor, which is disposed around the periphery of the die and provided with electrical terminals.
U.S. Pat. No. 4,808,009 A discloses an integrated sensing device including a resistance temperature sensor formed in a semiconductor substrate, and a resistance heater, which is formed on an insulating layer covering the substrate surface.